The Kramer PS-16DN is a stand alone redundant power supply for the Kramer VS-1616DN Modular Matrix Switcher. The Kramer VS-1616DN does come with its own power supply, but in high-traffic use environments, where users want to avoid any possible down time, they can purchase the PS-16DN as a redundant back up power supply to provide added protection in you Pro AV system and avoid system crashes.